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FAQ

Is vaccination effective in preventing staphylococcal mastitis in dairy heifers?

Studies have found that the two-dose label regimen of the licensed staphylococcal vaccine does not prevent new intramammary infection with Staph aureus or coagulase negative staphylococci. However, a different regimen suggests that early vaccinations followed by frequent boosters may decrease somatic cell counts and clinical severity.

Should farmers treat primiparous heifers with intramammary antibiotic before calving?

Some studies have recommended pre-calving use of intramammary infections in heifers; however, this practice should be evaluated on a farm by farm basis since there is a risk of antibiotic residues and the potential for inducing antimicrobial resistances in some bacteria.

I have heard that intramammary antibiotics are ineffective in the treatment of coliform mastitis. Does that mean that I should never used antibiotics in the treatment of these cases and only rely on supportive therapy?

The clinical signs we see with coliform mastitis are generally a results of inflammation stimulated by the release of lipopolysaccharides from the cell walls upon death of coliform bacteria. So by the time we see swelling and watery secretions, most of the bacterial population in the mammary gland has been killed by the cowâs own immune system. Intramammary antibiotics at that time will have little benefit. Multiple studies have evaluated the intramammary antibiotic treatment of clinical coliform mastitis against supportive treatment alone or against oxytocin. Return to clinical cure was similar among all groups. We do know, however, that cows with severe systemic signs (fever, dehydration, anorexia) are more likely to be endotoxaemic. In those cases, parenteral antibiotics (e.g. fluorochinolones) are recommended but intramammary antibiotics are unlikely to have much of an effect.

Our herd is faced with an outbreak of clinical mastitis and most cases have cultured positive for Klebsiella. We currently use sawdust for bedding but we are considering renovating stalls and using sand bedding. Will this eliminate our issue

Although inorganic bedding such as sand does not support the growth of coliform bacteria when clean, bedding with this material does not ensure freedom from these infections. Sand bedding can accumulate manure, urine, milk and other body fluids over time and essentially become âorganicâ with their addition, providing the necessary nutrients for bacterial growth. Inorganic bedding can help alleviate issues with coliform mastitis but is not a cure all. Managers still need to ensure that stalls are rebedded and groomed frequently and than alleys and cross-over areas are kept free of manure accumulation.

My bulk tank Somatic Cell Count (SCC) had been increasing; however, I see no clinical mastitis in my cows and my milk filter is clean. How can this be explained?

Some mastitis pathogens, most commonly the contagious pathogens Streptococcus agalactiae and Staphylococcusaureus, have become adapted to the udder environment and can survive within the udder without causing clinical signs. They, of course, stimulate a host response and quarter SCC may increase into the millions. High SCC quarters can only be detected with some manner of cell counting equipment (California Mastitis Test, Fossomatic methods, Delaval Cell Counter, etc) and then infection should be confirmed by culture.

Often the culture results of cows with high SCC are negative. Why is that the case ?

Negative culture results of cows with high SCC are frustrating. There are several reasons why this may happen though. First, the cow may have eliminated infection, and remaining high SCC is only a reflection of the recovery from the infection. Second, the cow still has an intramammary infection but the bacteria are shed in very low quantities or are shed intermittently and not detected in the bacteriological culture. Finally, the culture technique may not be able to identify the causal organism. Organisms that need special culture system include: Mycoplasma spp, Coxiella burnetii and viral infections.